1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive body, a manufacturing method of the same and a piezoelectric/electrostrictive element.
2. Description of the Related Art
Heretofore, a piezoelectric/electrostrictive element has been known as elements capable of controlling micro displacement on the order of submicrons. Especially, piezoelectric/electrostrictive elements which are each obtained by laminating, on a substrate made of a ceramic, a piezoelectric/electrostrictive portion formed of a piezoelectric/electrostrictive porcelain composition (hereinafter referred to simply as the “piezoelectric ceramic”) and an electrode portion to which a voltage is to be applied are suitable for control of the micro displacement. In addition, the piezoelectric/electrostrictive elements have excellent properties such as high electromechanical conversion efficiency, a high-speed response, a high durability and reduced power consumption. These piezoelectric/electrostrictive elements are applicable to various fields such as a piezoelectric pressure sensor, a probe movement mechanism of a scanning type tunnel microscope, a rectilinear guide mechanism disposed in an ultra-precision processing device, a servo valve for hydraulic control, a head of a VTR device, pixels constituting a flat panel type image display device and a head of an ink jet printer.
Also with regard to the composition of the piezoelectric ceramic constituting the piezoelectric/electrostrictive portion, various investigations have been made. For example, in recent years, there has been a tendency towards minimizing influences on the global environment such as the problem of the dissolution of lead (Pb) due to acid rain. Therefore, as a piezoelectric/electrostrictive ceramic in consideration of the influences on the environment, an (LiNaK)(NbTa)O3-based piezoelectric ceramic capable of providing a piezoelectric body or a piezoelectric element indicating satisfactory piezoelectric/electrostrictive properties even without containing any lead (Pb) has been developed.
The piezoelectric ceramic is a ferroelectric body, and it is incorporated in an electronic device or the like and generally subjected to a polarization treatment in order to utilize its properties (piezoelectric properties). This polarization treatment is a treatment in which a high voltage is applied to the piezoelectric ceramic to align directions of spontaneous polarizations in a specific direction. This treatment, is performed by applying the voltage to the piezoelectric ceramic under appropriate temperature conditions and the like. That is, a plurality of domains are present owing to a bias of a charge due to the spontaneous polarization, and the piezoelectric ceramic is subjected to a polarization treatment in which directions of the domains of the ferroelectric body are aligned in a constant direction for use.
In addition, the piezoelectric material (a ferroelectric material) is an aggregate of the domains, and the domains are classified into 180° domains and non-180° domains. Among the domains, the 180° domains contribute little to a strain, and the non-180° domains largely contribute to the strain. This is because the non-180° domain involves rotation of the domain which increases a volume change. Moreover, during the above-mentioned polarization treatment, the rotation of the non-180° domain occurs, and a large strain is generated.
However, the rotation of the non-180° domain, especially a 90° domain which indicates a large volume change has intense irreversibility. Therefore, once the polarization treatment in which the ceramic is retained at a high voltage is performed, the strain is reduced as compared with the strain generated during the polarization treatment. To solve the problem, a piezoelectric material in which reversibility of the domain rotation is intensified to exhibit a huge electrostrictive effect is disclosed (Patent Document 1).
[Patent Document 1] Japanese Patent Application Laid-Open No. 2004-363557
However, according to a manufacturing method of Patent Document 1, many days (five days to three months) are required for an aging treatments. Therefore, the method is inefficient, and an increase of a manufacturing cost is incurred.